There are many electrical devices such as environmental monitors and alarms which are installed at remote locations where they cannot, in many cases, be conveniently wired to electrical power lines. Batteries have limited lives and solar cells are expensive and don't work when the sun doesn't shine. Many remote applications, such as ocean surfaces or remote roadways, have available considerable mechanical energy that is not being used. That mechanical energy is normally in the form of essentially linear, bi-directional motion.
Almost all electrical power produced in the world is generated from large rotary generators. Some attempts have been made to convert linear mechanical energy into electricity. U.S. Pat. No. 4,239,974 would attempt to convert vehicular roadway traffic energy into electrical power by using a plurality of magnets and coils. This device, however, was impractical requiring extensive installation cost, and would have been very inefficient, wasting most of the available mechanical energy in compression springs.
Another U.S. Pat. No. 4,260,901 attempted to convert the linear rise and fall of sea waves into electrical power. This device required complex mechanical linkages, and also converted the linear motion into rotary motion to generate its power.
Powerful rare earth magnets (for example Samarium-Cobalt, and Neodymium-Iron-Boron magnets) have been available for years.